msm: krait-regulator: Initialize headswitches for secondary CPUs

Create a function to be called very early (before the krait-regulator
driver probes) to switch a cpu in BHS mode. Since we have not yet
probed yet, use the base address passed in to do the necessary writes.

Change-Id: I1cb1659f1e31e52b9d209427887230ee922aef80
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>